Faced with a host of diplomatic challenges, from growing nuclear and missile threats from North Korea to shaky ties with the South, Prime Minister Shinzo Abe is pinning his hopes on the latest cabinet reshuffle to regain public trust in his government.

Japan has been able to carry forward talks with other countries as Abe has created a long-serving government by continuing to win national elections and strengthening the foundations of his administration, analysts said.

But after a series of scandals involving his cabinet members, as well as his own alleged misconduct, public approval rates have tumbled to the lowest since Abe returned to power in late 2012. In a nationwide poll by Kyodo News released in mid-July, public support for Abe’s Cabinet fell 9.1 points from the previous month to 35.8 per cent.

If Abe fails to regain public support, even after the reshuffle, and speculation grows that he will leave his office in the near future, Tokyo would lose its negotiating power on the diplomatic front, in turn harming national interests, analysts add.

In addition to North Korea and the prolonged rows with South Korea over historical issues, Japan faces many other foreign policy issues; the enhancement of relations with the United States, and territorial disputes with China and Russia.

On the back of his ruling bloc’s huge parliamentary majorities, Abe has built close ties with authoritarian leaders, such as US President Donald Trump and Russian President Vladimir Putin.

Watch: Abe’s long, awkward handshake with Trump

Until Abe began his second stint as prime minister in December 2012, Japan had seen six prime ministers, including Abe, since Junichiro Koizumi resigned as premier in September 2006. The frequent changes of Japanese leaders have been derided as a revolving door.

“It is very difficult for short-lived governments under weak political leaders to attain diplomatic breakthroughs,” political commentator Norio Toyoshima said.

Abe has become the third-longest-serving Japanese prime minister in the postwar era after Eisaku Sato, who was in power between 1964 and 1972, and Shigeru Yoshida, who worked as leader for a year beginning in May 1946 and then between 1948 and 1954.

During their terms in office, Yoshida regained Japan’s sovereignty in 1952 by signing the San Francisco Peace Treaty the previous year, ending the US occupation after the second world war, and Sato won back control of US-ruled Okinawa islands in 1972.

Abe secured Putin’s agreement on joint economic activities on Russian-held islands claimed by Japan, while bolstering the US-Japan alliance by forming an intimate friendship with Trump.

In December 2015, Abe’s government signed with the previous South Korean administration of President Park Geun-hye a deal under which Tokyo and Seoul agreed that the issue of Korean “comfort” women who were forced into Japan’s wartime military brothels was “resolved finally and irreversibly.”

“These results have not been achieved unless Japan has a long-serving government,” Toyoshima said, adding, “If Mr Abe quits, Japan’s diplomacy could be faced with an impasse.”

Kishida, seen as having ambitions to succeed Abe, is the second-longest-serving foreign minister in the postwar era.

Tatsuhiko Yoshizaki, chief economist at the Sojitz Research Institute, said that whoever Abe picked as foreign minister, Japan’s key diplomatic policies would continue to be decided at the prime minister’s office.

Abe has tried to shore up the function of the prime minister’s office to boost decision-making powers on diplomatic and security policies by setting up a US-modelled National Security Council.

“One of Mr Abe’s big achievements was to launch the Japanese version of the US National Security Council,” Yoshizaki said, adding Abe has laid the foundation for “diplomacy led by the prime minister’s office.”

Japan’s NSC was established in 2013, aimed at empowering the prime minister’s office to take the lead in crafting foreign and defence policy.

Under the framework, the prime minister, the chief cabinet secretary and the foreign and defence ministers meet at least twice a month to discuss foreign and security matters based on information gathered from various ministries and agencies.

“As the NSC has mapped out firm foreign and security policies, Prime Minister Abe’s government has been able to hold in-depth discussions with the United States, China, Russia and South Korea,” Yoshizaki said.

“If Mr Abe steps down, it is very uncertain whether the next prime minister can handle foreign policy issues as skillfully as Mr Abe,” he said.

The cabinet’s approval ratings have fallen since the ruling parties forced through a controversial law to penalise the planning of a range of crimes and allegations surfaced of favouritism by Abe in connection with the project to construct the new university department.

“When Abe served as prime minister for one year through September 2007, he was forced to resign one month after he reshuffled the cabinet, as he failed to restore public support,” political commentator Toyoshima said.

“If the same thing happens, the fate of Japan’s diplomacy may be changed as early as one month later.”